In general, wind power generation refers to converting kinetic energy of wind into mechanical energy by a turbine, and converting this into electric energy. Usually, it is converted into an energy amount proportional to the cube of wind speed and area of the turbine. Wind power generators are classified into horizontal-axis type and vertical-axis type according to the direction of the rotation axis. Currently, horizontal-axis wind power generators or propeller-type wind power generators are mainly used.
Horizontal-axis wind power generators seriously affect the mechanical structure by overheating or over-rotation when a strong wind of an over wind speed exceeding the rated wind blows. In order to prevent this, when a wind of over wind speed blows, various forms of over wind speed controlling apparatuses are used to allow the rotator and nacelle to deviate from the wind direction or to decrease the rotation number of rotation wings.
Big size wind power generators allow the rotator and nacelle to deviate from the wind direction electrically by signals from the wind vane or decrease the rotation force of rotation wings by controlling the pitch of the rotation wings.
Small size wind power generators allow the rotator and nacelle to deviate from the wind direction by tail wings. In other words, they allow the direction of the rotation wings to be aerodynamically perpendicular to the wind direction by a simple constitution of fixedly installing the rear wing part at the rear end of the shaft of the rotation wing. However, such system may be damaged because vibration is continuously applied to the tail wing every time the rotator and nacelle return to its original position after avoiding the wind direction, or may allow the hinge device to be damaged.
The pitch control method mainly controls the direction of the rotation rings so that they stand obliquely with respect to the wind direction by a sensing signal provided from a wind direction/wind speed sensing part for sensing the wind direction and wind speed. However, such method is mainly applied to large size wind power generators, and has not been applied to small size wind power generators due to cost problems and limitations in installing control apparatuses.
Meanwhile, the method for controlling the output of wind power generators can be classified into a controlling part of the generator, and a controlling part indirectly supporting the output of the generator by using the shape of wings. The latter, which is a method of limiting the rotation speed of wings by using aerodynamic properties of the wings of the rotator, is classified into a stall control type and a pitch control type. In this regard, the present invention applies the pitch control technique, which is a method for controlling torque by dropping the lift applied to the blade by controlling the pitch angle of the blade, to small size wind power generators.